It's no secret that word-of-mouth is one of the most effective types of marketing and that consumers trust other consumers more than they trust brands. According to Forrester Research, 70 percent of consumers trust reviews shared by friends on social media or elsewhere, while only 43 percent said they trust natural search engine results.

But search is changing, and as social media continues to become a crucial part of brand discovery, search engine optimization (SEO) is evolving to reflect an emphasis on good content and social engagement.

Google's SEO algorithms aren't what they used to be. The search engine giant has gone back and forth on whether social signals, such as retweets and Facebook likes, directly affect page rankings. In 2010, Matt Cutts, head of Google's Webspam team, said the company was taking social signals into account, but he had a different take earlier this year.

"Facebook and Twitter pages are treated like any other pages in our Web index, so if something occurs on Twitter or occurs on Facebook and we're able to crawl it, then we can return that in our search results," he said in a recent Webmaster help video. "But as far as doing special specific work to sort of say 'you have this many followers on Twitter or this many likes on Facebook,' to the best of my knowledge, we don't currently have any signals like that in our Web search ranking algorithms," he added.

Still, experts maintain that social media has always had an impact on SEO, and that its impact is only growing. Since the introduction of Google's Panda, Penguin, and Hummingbird search algorithms, which affect roughly 90 percent of online searches, rankings have gotten more sophisticated. In the early days of SEO, quantity trumped quality, and sprinkling irrelevant links or redundant keywords on a site could place a page higher up in the search results. Today's algorithms protect consumers from that type of ranking manipulation.

"Google has always valued good content, but the metrics that determine what constitutes good content have changed," Nate Elliot, vice president and principal analyst at Forrester, says. "Today, if a piece of content performs well on social media and gets lots of shares or goes viral, that's a good indication that it'll rank highly in search results as well."

Google hasn't denied this correlation, Elliot says. Rather, Google doesn't want to suggest that just because a brand has a million followers